border-bottom-1px($color)
  position: relative
  &::after
    display: block
    content: ''
    position: absolute
    left: 0
    bottom: 0
    width: 100%
    border-bottom:1px solid $color
border-top-1px($color)
  position: relative
  &::after
    display: block
    content: ''
    position: absolute
    left: 0
    top: 0
    width: 100%
    border-top:1px solid $color
border-none()
  &::after
    display: none
bg-image($url)
  background-image: url($url + '@2x.png')
  @media (min-device-pixel-ratio: 3),(-webkit-min-device-pixel-ratio: 3)
    background-image: url($url + '@3x.png')